Multiple gear stage automatic transmission

ABSTRACT

A multiple stage transmission in planetary design comprises three planetary gear sets (P 1 , P 2 , P 3 ), at least six rotatable shafts ( 1, 2, 3, 4, 5, 6 ), the same as brakes ( 03, 04 ) and clutches ( 14, 15, 36, 56 ), the drive shaft ( 1 ) is permanently connectable with the ring gear of the first planetary gear set (P 1 ) and via one clutch ( 15 ) with the shaft ( 5 ) which is connected with the sun gear of the second planetary gear set (P 2 ) and via the clutch ( 56 ) connectable with the shaft ( 6 ), the shaft ( 6 ) being connected on one side with the spider of the first planetary gearset (P 1 ) and, on the other side, loosely connectable via one clutch ( 36 ) with the shaft ( 3 ) which is permanently connected with the spider of the second planetary gear set (P 2 ) and the spider of the third planetary gear set (P 3 ) and via one brake ( 03 ) attachable to the housing (G), the driven shaft ( 2 ) being connected with the ring gear of the third planetary gear set (P 3 ) and the ring gear of the second planetary gear set (P 2 ), the shaft ( 4 ) being permanently connected with the sun gear of the third planetary gear set (P 3 ), via one clutch ( 14 ) loosely connectable with the drive shaft ( 1 ) and via one brake ( 04 ) attachable to the housing (G) and the sun gear of the first planetary gear set (P 1 ) being non-rotatably connected via one shaft ( 0 ) with the housing (G).

According to the preamble of claim 1, the invention concerns a multiple stage transmission, particularly an automatic transmission for a motor vehicle.

In the prior art, automatic transmission, particularly for motor vehicles, comprise planetary gear sets shifted by means of friction and shifting elements such as clutches and brakes and usually have one starting element, such as a hydrodynamic converter or a fluid clutch, optionally provided with a lock-up clutch and subject to a slip effect.

Such a transmission results from EP 0 434 525 A1. It essentially comprises one drive shaft and one driven shaft disposed parallel with each other, one double planetary gear set disposed concentrically with the driven shaft and five shifting elements in the form of three clutches and two brakes, the optional locking of which by pairs determines the different gear ratios between the drive shaft and the driven shaft. This transmission has a front-mounted range change set and two power paths so that six forward gears are obtained by selective engagement by pairs of the five shifting elements.

Here two clutches are needed in the first power path for transmitting the torque from the front-mounted range change set to two elements of the double planetary gear set. These are situated in the power flow direction essential downstream of the front-mounted range change set in the direction of the double planetary gear set. In the second power path, one other clutch is provided which loosely connects it with another element of the double planetary gear set. The clutches are arranged here so that the internal disc carrier constitutes the output.

In addition, the U.S. Pat. No. 6,139,463 publication has disclosed a compact multiple stage transmission of a planetary design, particularly for motor vehicles, which has two planetary gear sets and one front-mounted range change set, the same as three clutches and two brakes. In this known multiple stage transmission, two clutches C-1 and C-3 are provided in a first power path for transmitting the torque from the front-mounted range change set to the two planetary gear sets. The external disc carrier or the cylinder or piston and pressure compensation side of the clutch C-3 is here connected with a first brake B1. Besides, the internal disc carrier of the third clutch C-3 is connected with the cylinder or piston and pressure compensation side of the first clutch C-1, the internal disc carrier of the first clutch C-1 is located on the output side and connected with a sun gear of the third planetary gear set.

From the Applicant's DE 199 49 507 A1 is further known a multiple stage transmission where two non-shiftable front-mounted range change sets are provided on the drive shaft which, on the output side, produce two rotational speeds which, together with the rotational speed of the drive shaft, are optionally shiftable by selective engaging of the used shifting elements, to a shiftable double planetary gear set acting upon the driven shaft in a manner such that to change over from one gear to the next sequential higher or lower gear of the two specifically actuated shifting elements, respectively, only one shifting element has to be engaged or disengaged.

From DE 199 12 480 A1 is known an automatically shiftable motor vehicle transmission having three spider planetary gear sets, the same as three brakes and two clutches, for shifting six forward gears and one reverse gear and having one drive shaft and one driven shaft. The automatically shiftable motor vehicle transmission is designed so that the drive shaft is directly connected with the sun gear of the second planetary gear set and the drive shaft is connectable, via the first clutch, with the sun gear of the first planetary gear set and/or via the second clutch with the spider of the first planetary gear set. Additionally or alternatively, the sun gear of the first planetary gear set is connectable, via the first brake, with the housing of the transmission and/or the spider of the first planetary gear set with the housing, via the second brake, and/or the sun gear of the third planetary gear set with the housing via the third brake.

DE 102 13 820 A1 has also disclosed a multiple stage automatic transmission comprising one first input path T1 of a first reduction ratio; one input path T2 which has a higher reduction ratio than said input path T1; one planetary gear set having four elements, said four elements being one first element, one second element, one third element and one fourth element in the sequence of elements in a rotational speed diagram; one clutch C-2 which transmits rotation of the input path T2 to the first element S 3; and clutch C-1 which transmits the rotation from the input path T2 to the fourth element S2; one clutch C-4 which transmits rotation from the input path T1 to the first element; one clutch C-3 which transmits rotation from the input path T1 to the second element C-3; one brake B-1 which creates engagement of the fourth element; one brake B-2 which creates engagement of the second element; and one output element coupled with the third element R3.

With the scope of the Applicant's DE 101 15 983 A1 is described a multiple stage transmission having one drive shaft connected with a front-mounted range change set, one driven shaft connected with a rear-mounted range change set and having a maximum of seven shifting elements by the optional shifting of which at least seven forward gears can be shifting without group shift. The front-mounted range change set is formed by a front-mounted planetary gear set or a maximum of two non-shiftable front-mounted planetary gear sets coupled with the front-mounted planetary gear set, the rear-mounted range change set is designed as a two-spider-four shaft transmission with two shiftable rear-mounted range change sets and four free shafts. The first free shaft of said two-spider-four shaft transmission is connected with the first shifting element, the second free shaft with the second and third shifting elements, the third free shaft with the fourth and fifth shifting elements and the fourth free shaft is connected with the driven shaft. For a multiple stage transmission with a total of six shifting elements, the invention additionally proposes to connect the third free shaft or the first free shaft of the rear-mounted range change set with a sixth shifting element. For a multiple stage transmission having a total of seven shifting elements, the invention proposes connecting the third free shaft additionally with a shift shifting element D′ and the first free shaft additionally with a seventh shifting element.

Within the scope of the Applicant's DE 101 15 987 has been described a multiple stage transmission having at least seven gears. Said transmission, together with the drive shaft and the driven shaft, comprises one non-shiftable front-mounted range change set and one shiftable rear-mounted range change set in the form of a two-spider-four shaft transmission. The front-mounted range change set comprises one first planetary gear set which, together with the input rotational speed of the drive shaft, offers a second rotational speed which can optionally be shifted to a rear-mounted range change set. The rear-mounted range change set consists of two shiftable planetary gear sets which, with the six shifting elements, can shift at least seven gears, with two power paths being formed. At the same time, group shifts are always advantageously prevented during each shifting operation. One 9-gear multiple stage transmission has further become known from DE 29 36 969; it comprises eight shifting elements and four gear sets.

Automatically shiftable vehicle transmissions of a planetary design have already generally been widely described in the prior art and are subject to permanent developments and improvement. Said transmissions thus must have a sufficient number of forward gears, the same as one reverse gear and a ratio very well suited for motor vehicles with a high total spread and favorable ratio ranges. They must also make possible a high starting ratio in a forward direction and contain a direct gear, the same is adequate for use both in passenger and in commercial vehicles. In addition, said transmission must have low construction cost, especially require a low number of shifting elements and prevent double shifts in a sequential shifting mode so that in case of shiftings in defined gear groups only one shifting element is changed.

The problem on which this invention is based is to propose a multiple stage transmission of the above mentioned type where the construction cost is optimized and besides the efficiency degree in the main drive gears is improved with regard to towing and gearing losses. Furthermore, in the inventive multiple stage transmission, low torques act on the shifting elements and planetary gear sets and the rotational speeds of the shafts, shifting elements and planetary gear sets are kept low. In addition, the number of gears and the transmission spread are to be increased so that advantageously seven or eight gears and at least one reverse gear, preferably two reverse gears, can be implemented. The inventive transmission must also be adequate for any design of a vehicle, particularly for a front-transverse arrangement.

According to the invention, said problem is solved by the features of claim 1. Other advantages and advantageous developments result from the sub-claims.

The invention accordingly proposes a multiple stage transmission of planetary design which has one drive shaft and one driven shaft located in one housing. In addition, also provided are at least three planetary gear sets, at least six rotatable shafts, the same as at least six shifting elements including brakes and clutches, the selective engagement of which by pairs produces different reduction ratios between the drive shaft and the driven shaft so that preferably eight forward gears and at least one reverse gear can be implemented.

The drive shaft is permanently connectable with the ring gear of the first planetary gear set and via one clutch with a fifth shaft which is connected with the sun gear of the second planetary gear set and connectable via one clutch with a sixth shaft, said sixth shaft being connected on one side with the spider of the first planetary gear set and, on the other side, loosely connectable via a clutch with a third shaft which is permanently connected with the spider of the second planetary gear set and the spider of the third planetary gear set and via one brake attachable to the housing. Besides, the driven shaft is connected with the ring gear of the third planetary gear set and the ring gear of the second planetary gear set, one fourth shaft being permanently connected with the sun gear of the third planetary gear set, via one clutch loosely connectable with the drive shaft and via one other brake attachable to the housing and sun gear of the first planetary gear set being non-rotatably connected with the housing.

By the inventive configuration of the multiple stage transmission, particularly for passenger motor vehicles, suitable ratios and a considerable increase in the total spread of the multiple stage transmission results whereby an improvement in driving comfort and a significant reduction in consumption are produced.

With the inventive multiple stage transmission, the construction cost is furthermore considerably reduced due to a small number of shifting elements, preferably two brakes and four clutches. It is advantageously possible with the inventive multiple stage transmission, to start off with a hydrodynamic converter, an external starting clutch or with any other suitable external starting element. It is also conceivable to have a starting off operation with one starting element integrated in the transmission. Preferably suitable is a shifting element actuated in the first forward gear and in the first reverse gear.

With the inventive multiple stage transmission, a good degree of efficiency in the main drive gears relative to towing and gearing losses further results.

Besides, torque in the shifting elements and in the planetary gear sets of the multiple stage transmission is low whereby the wear is advantageously reduced in the multiple stage transmission. The low torque also makes correspondingly small dimensions possible whereby the installation space needed and the attendant costs are reduced. In addition, the rotational speeds are also low for the shafts, the shifting elements and the planetary gear sets.

The inventive transmission is furthermore designed so that an adaptability to different drive line configurations is possible both in power flow direction and with regard to space.

Herebelow the invention is explained in detail by way of example with reference to drawings which show:

FIG. 1 is a diagrammatic view of a preferred embodiment of an inventive multiple stage transmission suitable for a front-transverse construction;

FIG. 2 is a configuration diagram by way of example of the inventive multiple stage transmission according to FIG. 1; and

FIG. 3 is a configuration diagram by way of example for the inventive multiple stage transmission according to FIGS. 1 and 2.

In FIG. 1, an inventive multiple stage transmission is shown having one drive shaft 1 (An) and one driven shaft 2 (Ab) located in one housing G.

Three planetary gear sets P1, P2, P3 are provided. The first and second planetary gear sets P1 and P2 are preferably designed as minus planetary gear sets; the first planetary gear set serves as front-mounted range change set; the third planetary gear set is designed as a plus planetary gear set and, with the second planetary gear set P2, constitutes the main gear set.

As can be seen from FIG. 1, only six shifting elements are provided, namely, two brakes 03, 04 and four clutches 14, 15, 36 and 56.

With said shifting elements, a selective shifting of eight forward gears and preferably two reverse gears can be implemented. The inventive multiple stage transmission has a total of six rotatable shafts, namely, the shafts 1, 2, 3, 4, 5 and 6.

In the multiple stage transmission according to FIG. 1, it is inventively provided, that the input takes place by the shaft 1 which is permanently connected with the ring gear of the first planetary gear set P1 and connectable, via one clutch 15, with the shaft 5 which is connected with the sun gear of the second planetary gear set P2 and connectable, via the clutch 56, with the shaft 6 which, on one side, is connected with the spider of the first planetary gear set P1 and, on the other side, loosely connectable, via a clutch 36, with a shaft 3 which is permanently connected with the spider of the second planetary gear set P2 and the spider of the third planetary gear set P3. Besides, the shaft 3 is attachable via one brake 03 to the housing G. The clutches 56 and 36 are preferably disposed side by side. Within the scope of a preferred embodiment, they have a common external disc carrier situated on the input side. The clutch 36 is preferably situated in power flow direction behind the clutch 56.

In addition, the drive shaft 1 is loosely connectable via one clutch 14 with the shaft 4 which is attachable to the housing G via one brake 04 and connected with the sun gear of the third planetary gear set P3. The clutches 14 and 15 are, likewise, preferably disposed side by side and can have a common external disc carrier situated on the input side. The clutch 14 is preferably situated in power flow direction behind the clutch 15.

The output inventively takes place via the shaft 2 which is connected with the ring gear of the third planetary gear set P3 and the ring gear of the second planetary gear set P2. Besides, the sun gear of the first planetary gear set is non-rotatably connected via one shaft 0 with the housing G.

The spatial arrangement of the shifting elements can be arbitrary, limited only by the dimensions and the outer molding. As is to be determined from FIGS. 1 and 2, the clutches 56, 36, 14, 15, preferably observed radially, are situated approximately above the planetary gear sets; and other arrangements being also possible.

The embodiment, according to FIG. 2, differs from the embodiment according to FIG. 1 in that one freewheel FD is provided parallel with the brake 04. Thereby high supporting torques can be reduced.

A variation (not shown) provides that the second planetary gear set P2 with the third planetary gear set P3 is combined or reduced to form one Ravigneaux set with common spider and common ring gear. Compared with the above described, this design has the advantage that less parts are needed.

In FIG. 3 is shown, by way of example, a configuration diagram of the inventive multiple stage transmission according to FIGS. 1 and 2. For each gear, two shifting elements are engaged. From the configuration diagram can be deduced the respective ratios i of the individual gear steps and the ratio ranges to be determined therefrom. It can also be determined from the configuration diagram that in sequential shifting mode, double shifts or group shifts are prevented since two adjacent gear steps use one shifting element in common. As can be seen from the configuration diagram, it is also possible to skip over gears without group shift. The eighth gear is preferably designed as a direct gear, the ratio ranges being small in the upper gears. The configuration diagram is especially adequate for passenger cars. The transmission can also be designed as a seven-gear transmission when the seventh gear falls so that the ratio steps 1.27 and 1.1 are combined.

For the first three gears, the brake 04 is always closed. In addition, the clutch 56 for first gear, the clutch 15 for second gear and the clutch 36 for third gear are engaged. For the gears four, five and six, the clutch 36 is always engaged. Besides, the clutch 15 for fourth gear, the clutch 56 for fifth gear and clutch 14 for sixth gear are engaged. The seventh gear results by closing the clutches 14 and 56 and the eighth gear by engaging the clutches 14 and 15. The brake 03 and the clutch 15 for the first reverse gear and the brake 03 and the clutch 56 for the second reverse gear are engaged.

According to the invention, it is possible to start-off with an integrated shifting element (IAK). The clutch 56 is especially suitable since, it is used in the first gear and in the reverse gear without reversal in direction of rotation. A reversal between the reverse gears is possible without group shift which is advantageous for safety vehicles, for example.

According to the invention, different gear ratios can result with the same transmission diagram in conformity with shifting logic so that a variation in use specific to the vehicle is made possible.

It is further possible to provide on each adequate plane of the multiple stage transmission additional freewheels such as between one shaft and the housing or in order optionally to connect two shafts.

On the input side or on the output side, one axle differential and/or one transfer differentials can be situated according to the invention.

Within the scope of an advantageous development, the drive shaft 1 can be separated, as needed, from a prime mover by a clutch element, it being possible to use a hydrodynamic converter, a hydraulic clutch, a dry starting clutch, a wet starting clutch, a magnetic powder clutch, or a centrifugal clutch as a clutch element. It is also possible to place such a starting element in a power flow direction downstream of the transmission in which case the drive shaft 1 is permanently connected with the crankshaft of the motor.

The inventive multiple stage transmission besides makes possible placing one torsional vibration damper between the motor and the transmission.

Within the scope of another embodiment of the invention, not shown, it is possible to situate a wear-free brake, such as a hydraulic or electric retarder or the like, upon each shaft, preferably upon the drive shaft 1 or the driven shaft 2, which is especially important for use in commercial vehicles. It is also possible to provide one power take-off on each shaft, preferably on the drive shaft 1 or the driven shaft 2 for driving additional units.

The used shifting elements can be designed as power shifting clutches or brakes. Especially force-locking clutches or brakes like multi-disc clutches, band brakes and/or tapered clutches can be used. Besides, form-locking brakes and/or clutches, such as synchronizers or dog clutches, can also be used as the shifting elements.

Another advantage of the multiple stage transmission introduced here is that an electric machine can be mounted upon each shaft as generator and/or as an additional prime mover, upon each shaft.

Every constructional design, especially every spatial arrangement of the planetary gear sets and of the shifting elements per se the same as relative to each other and insofar as technically convenient, obviously falls under the scope of protection of the instant claims without affecting the operation of the transmission such as indicated in the claims even if said designs are not explicitly shown in the Figures or in the description. Reference numerals 0 shaft 36 clutch 1 shaft 56 clutch 2 shaft P1 planetary gear set 3 shaft P2 planetary gear set 4 shaft P3 planetary gear set 5 shaft An drive 6 shaft Ab drive 03 brake i ratio 04 brake G housing 14 clutch ED freewheel 15 clutch 

1-30. (CANCELED).
 31. A multiple stage transmission in planetary design, particularly for an automatic motor vehicle, comprising housing (G) accommodating a drive shaft (1) and a driven shaft (2), first, second and third planetary gear sets (P1, P2, P3), at least the drive shaft, the driven shaft, a third shaft, a fourth shaft a fifth shaft and a sixth shaft (1, 2, 3, 4, 5, 6), at least six shifting elements (03, 04, 14, 15, 36, 56) including first and second brakes (03, 04) and first, second, third and fourth clutches (14, 15, 36, 56) which are selectively engageable for producing different reduction ratios between the drive shaft (1) and the driven shaft (2) so that the multiple stage transmission is able to implement either seven or eight forward gears and at least one reverse gear, the drive shaft (1) being permanently connectable with a ring gear of a first planetary gear set (P1) and via the second clutch (15) with the fifth shaft (5) which is connected with a sun gear of a secondary planetary gear set (P2) and via the fourth clutch (56) connectable with the sixth shaft (6); the sixth shaft (6), on a first side, being connected with a spider of the first planetary gear set (P1) and, on another side, being loosely connectable, via the third clutch (36) with the third shaft (3), which is permanently connected with a spider of the second planetary gear set (P2) and with a spider of the third planetary gear set (P3) and attachable, via one brake (03), to the housing (G), the driven shaft (2) being connected with a ring gear of the third planetary gear set (P3) and a ring gear of the second planetary gear set (P2), the fourth shaft (4) being permanently connected with a sun gear of the third planetary gear set (P3), via a first clutch (14) loosely connectable with the drive shaft (1) and via the second brake (04) attachable to the housing (G) and a sun gear of the first planetary gear set (P1) being non-rotatably connected with the housing(G) via another shaft (0).
 32. The multiple stage transmission according to claim 31, wherein the seven or eight forward gears are shiftable so that during a change from one forward gear to one of a next subsequent higher or a next subsequent lower forward gear, only one previously engaged shifting element is disengaged and only one previously unengaged shifting element is engaged.
 33. The multiple stage transmission according to claim 31, wherein two shifting elements are respectively engaged in the seven or eight forward gears and in the at least one reverse gear.
 34. The multiple stage transmission according to claim 31, wherein the second brake and the fourth clutch (04, 56) are engaged in the first forward gear, the second brake and second clutch (04, 15) are engaged in the second forward gear, the second brake and the third clutch (04, 36) are engaged in the third forward gear, the second and the third clutches (15, 36) are engaged in the fourth forward gear, the third and the fourth clutches (36, 56) are engaged in the fifth forward gear, the first and the third clutches (14, 36) are engaged in the sixth forward gear, the first and the third clutches (14, 36) are engaged in the seventh forward gear, and the first and the second clutches (14, 15) are engaged in the eighth forward gear.
 35. The multiple stage transmission according to claim 31, wherein the multiple stage transmission has two reverse gears.
 36. The multiple stage transmission according to claim 35, wherein during a change gear change from one of the two reverse gears to the other of the two reverse gears only one previously engaged shifting element is disengaged and one previously unengaged shifting element is engaged.
 37. The multiple stage transmission according to claim 31, wherein the first brake (03) and one of the second and fourth clutches (15, 56) are engaged in a reverse gear.
 38. The multiple stage transmission according to claim 31, wherein at least one of the first and second clutches (14, 15) and the third and fourth clutches (36, 56) are respectively disposed side by side.
 39. The multiple stage transmission according to claim 31, wherein at least one of the first and second clutches (14, 15) and the third and fourth clutches (36, 56) respectively have a common external disc carrier.
 40. The multiple stage transmission according to claim 31, wherein at least one of an external disc carrier of the first and second clutches (14, 15) and an external disc carrier of the third and fourth clutches (36, 56) is located on an input side.
 41. The multiple stage transmission according to claim 31, wherein the first and the second planetary gear set (P1, P2) are minus planetary gear sets and the third planetary gear set (P3) is a plus planetary gear set.
 42. The multiple stage transmission according to claim 31, wherein the second planetary gear set (P2) and the third planetary gear set (P3) are associated with a Ravigneaux set by a common spider gear and a common ring gear.
 43. The multiple stage transmission according to claim 31, wherein the multiple stage transmission has at least one additional freewheel.
 44. The multiple stage transmission according to claim 43, wherein the at least one additional freewheel is located between one of the drive shaft, the driven shaft, the third shaft, the fourth shaft, the fifth shaft, the sixth shaft (1, 2, 3, 4, 5, 6) and the housing (G).
 45. The multiple stage transmission according to claim 31, wherein an input side and an output side of the multiple stage transmission are provided on the same side of the housing (G).
 46. The multiple stage transmission according to claim 31, wherein one of an axle and a transfer differential is provided upon one of an input side and an output side of the multiple stage transmission.
 47. The multiple stage transmission according to claim 31, wherein one of the clutch elements facilitates separating the drive shaft (1) from a prime mover of the multiple stage transmission.
 48. The multiple stage transmission according to claim 47, wherein one of a hydrodynamic converter, a hydraulic clutch, a dry starting clutch, a wet starting clutch, a magnetic powder clutch, and a centrifugal clutch is provided as the clutch element.
 49. The multiple stage transmission according to claim 47, wherein the drive shaft (1) is fixedly connected with a crankshaft of a prime mover and an external starting element is provided in a power flow direction downstream of the multiple stage transmission.
 50. The multiple stage transmission according to claim 31, wherein the drive shaft (1) is fixedly connected with a crankshaft of a prime mover and a starting element of the transmission facilitates starting of the multiple stage transmission.
 51. The multiple stage transmission according to claim 50, wherein the fourth clutch (56) is used as starting element for starting the multiple stage transmission.
 52. The multiple stage transmission according to claim 31, wherein a torsional vibration damper is located between a prime mover and the multiple stage transmission.
 53. The multiple stage transmission according to claim 31, wherein a wear-free brake is provided on each shaft of the multiple stage transmission.
 54. The multiple stage transmission according to claim 31, wherein a power take-off is provided upon at least one of the drive shaft, the driven shaft, a third shaft, a fourth shaft, a fifth shaft and a sixth shaft (1, 2, 3, 4, 5, 6) for driving an additional unit.
 55. The multiple stage transmission according to claim 31, wherein a power take-off is provided upon one of the drive shaft (1) and the driven shaft (2).
 56. The multiple stage transmission according to claim 55, wherein each shifting element is one of a power shifting clutch and a power shifting brake.
 57. The multiple stage transmission according to claim 31,wherein each shifting element is one of a multi-disc clutch, a band brake and a tapered clutch.
 58. The multiple stage transmission according to claim 31, wherein each shifting element is one of a form-locking brake and a form-locking clutch.
 59. The multiple stage transmission according to claim 29, wherein an electric machine is mounted on at least one of the drive shaft, the driven shaft, the third shaft, the fourth shaft, the fifth shaft and the sixth shaft (1, 2, 3, 4, 5, 6) and functions as one of a generator and an additional prime mover.
 60. The multiple stage transmission according to claim 31, wherein at least one of the first clutch and the second clutch (14, 15) and the third clutch and the fourth clutch (36, 56) are located approximately above the planetary gear sets (P1, P2, P3) when radially observed. 